AUTOMATIC LDR LIGHT SCHEMATIC DIAGRAMSince the non-inverting reference frequency is higher than the inverting input voltage, the IC ouput value is ’1'. Transistor in ‘ON’ state, relay is also ‘ON’, thus the AC light will be close and the light turns on.

When it’s bright or the resistor value of LDR is low, the current is high. Since the inverting input voltage is higher than the non inverting reference voltage, the IC output is ’0', transistor in ‘OFF’ state, thus the AC open and the light turns off.